The demand for freshwater is on a constant rise, and consequently, so is the awareness to conserve fresh water. One of the ways to conserve freshwater is to use water drain systems that do not require flush with water. Using water free urinals is a good example of a water saving solution. The idea of water free drains has been contemplated by many inventors. The basic problems flush free urinals have to solve is passing urine to the sewer pipes without leaving an exposed we area where microbes can develop, while preventing urine odors from escaping into the air of the living spaces, and complying with plumbing regulations that demand that the flow of liquids through a trap may not be obstructed (or made potentially vulnerable to obstruction).
In order to address these problems, existing flush free urinals utilize a variation of a U-shaped trap that collects urine in a compartment while minimizing the contact between the collected urine and the surrounding air. Whereas, other types of urinals additionally use a sealant liquid, that is typically an oily substance that floats over the urine in a drain trap and prevents passing of odors from the urine into the air in the inhabitable spaces, see for instance Atwill (U.S. Pat. No. 6,589,440 B2) and Gorges (U.S. Pat. No. 6,053,197).
The liquid sealant approach is more efficient at blocking odors from escaping into the surrounding air. However, the sealant liquid partially mixes with urine at each use, and a portion of it passes to the sewer pipe with each use. Furthermore, if the urinal is infrequently used, the urine evaporates in between uses, allowing a portion of the sealant liquid to pass from the inlet side of the trap to the outlet side of the trap, and on the next use a more substantial portion of the sealant liquid is lost. Therefore, if the urinal is not frequently used, is requires more frequent replenishment of the sealant liquid, thus raising the burden and cost of maintenance.
Furthermore, in order to minimize the loss of liquid sealant in existing water free traps, the turbulence caused by incoming urine into the urinal has to be minimized. Thus, the flow rate through existing traps is kept at a minimum. The latter bring another drawback to existing water free urinals, which is the accumulation of solid waste in the trap, also leading to a necessity for frequent maintenance.
Due to the above drawbacks, despite the potential for significant water saving, current flush free urinals have not been widely adopted. The reason for the lack of widespread adoption may be attributed to a lack of performance for some types of flush free urinals, and/or the relatively high maintenance cost for other types of urinals. For example some flush free urinals do not reduce the smell of urine to a comfortable level. On the other hand, existing urinals that utilize a liquid sealant require a relatively frequent maintenance schedule. The sealant liquid is lost due to normal use and must be replenished after a certain number of uses. Additionally, the least the urinal is used the higher the loss of liquid sealant per use, and the more often the liquid sealant has to be replenished.
Gorges (U.S. Pat. No. 6,973,939) describes a cartridge type for hosting the sealant liquid, and working as a trap. The latter approach allows for an easy replacement of the cartridge. However, given the draw backs of the sealant liquid discussed above, the cost of frequent replacement of a cartridge is also prohibitive to the point of exceeding the cost of using water to flush the urinal. Because of the maintenance cost, liquid sealant based type urinals is mostly beneficial in places with very high frequency of use.
Therefore, there is a need for an economical system for disposing of waste liquids without requiring flushing, while keeping a odor sealant in the trap when the urinal is not used, or infrequently used, and can be easily maintained.